Update stopps at x Check for expected files

When trying to update 19.0.13 → 20.0.14, the update stops at first step “x Check for expected files”. No more debug info… Where can I found out what’s the problem here?

Info: I just updated from further version, so no files should be missing.
In first try update runned until the download, but the download was blocked by nextCloud download server… now Im stuck in the first step -.-